BAJADA DEL DIABLO IMPACT CRATER-STREWN FIELD (ARGENTINA): GROUND MAGNETIC AND ELECTROMAGNETIC SURVEYS

PREZZI, CLAUDIA; ORGEIRA, MARÍA JULIA; ACEVEDO, R.D.; PONCE, JUAN FEDERICO; MARTÍNEZ, ÓSCAR; VÁSQUEZ, CARLOS; CORBELLA, HUGO; GONZÁLEZ GUILLOT, M.; RABASSA, JORGE

BOLLETTINO DI GEOFISICA TEORICA ED APPLICATA

ISTITUTO NAZIONALE DI OCEANOGRAFIA E DI GEOFISICA

Año: 2010 vol. 51 p. 121 - 124

0006-6729

Total magnetic field was measured at 1563 stations located in and out of craters A and 8, using a Geometrics 856 proton precession magnetometer. The obtained data were corrected for the diurnal variations in the Earth’s magnetic field and the IGRF value was subtracted. Basalts boulders, sandy matrix and infilling sediments were collected, and the corresponding magnetic susceptibilities were measured; the intensity of the remanent magnetization of basalt boulders was also measured. 20 profiles were surveyed at crater 8 with a GEM-2 small broadband electromagnetic sensor using 5 different frequencies. Detailed crater topography was determined using a total station. 726 topographic points were surveyed in craters A and 8.The magnetic anomalies show a circular pattern with magnetic lows (-100 to -200 nT) in the crater’s floors, characteristic of impact structures. Furthermore, in the crater’s rims, high-amplitude, conspicuous and localized (short wavelength) anomalies, ranging between 2000 and -1500 nT, are observed. Such large amplitude and short wavelength anomalies are not detected out of the craters. Euler’s deconvolution was applied in order to estimate the depth of the sources. The first and the second vertical derivatives, the analytic signal and the curvature attributes of the residual magnetic field, were also calculated with the aim of sharpening and further analyse the detected anomalies. 2.5 and 3D modelling were carried out, considering the existence of induced and remanent magnetizations.The morphological, geological and geophysical features of the studied circular structures could only be satisfactorily explained assuming an extra-terrestrial projectile impact.